Bank of Pipes in trench, and encased or concrete formwork

– Spacers are used to prevent the pipe bank from drifting, or floating from the concrete pour. 

– The use of bricks or wood is not recommended, as these materials can deform the duct wall.

–The base of the spacer serves to provide sufficient clearance in the trench floor to allow concrete to the specified thickness at the bottom of the casing.


You must ensure that the entire bank of ducts runs as straight as possible from manhole to manhole.

Once the duct bank is straight, it needs to be anchored to prevent movement when the concrete is poured.

Movement can be caused by buoyancy of the ducts, shaking of the concrete, and vibration.
It is recommended to incorporate reinforcing rods that are buried in the trench floor to secure the duct bank and to prevent movement during concrete placement.
In areas where ground conditions make it impossible to bury a rod deep enough for effective anchoring, it is recommended that a mechanical trench jack be placed over the location of the spacers and adjusted downward to support the duct bank. to the bottom of the ditch.

Separation of Tubes

Underground Electrical Distribution Network

In a bank of tubes for electricity conduction, the tubes must be separated from each other, due to 3 reasons:

1.- To provide adequate heat dissipation generated by the cables inside the tube.

2.- To have a space that allows the concrete to completely cover each tube.

3.- To physically separate the tubes and replace a cable inside in case of failure.

Underground Distribution Telephone Network

En banco de tubos para comunicaciones, la separación entre tubos debe ser solo para tener un espacio que permita que el concreto cubra completamente cada tubo.


Spacers are used to prevent the pipe bank from drifting, or floating from the concrete pour.

The distance between separator cells varies according to the material of the tube, and the weight per meter of the cables it contains.

The separator cells are placed 1.5 to 2.4 meters apart.

Expansion/Contraction of tubes due to temperature changes

The tubes that form the underground wiring lines expand or contract due to changes in temperature.

When the temperature changes +/- 5.6° C, for every 30.5 meters the tubes expand or contract according to the material from which they are made:

– PVC tube: 3/8 inch (9.5 mm)

– High Density Polyethylene Tube: 1 inch (25.4 mm)

– RTRC (Reinforced Thermoset Resin Conduit): 1/8 inch (3.2 mm)

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